Electrical stimulation of neural tissue is becoming an increasingly preferred form of therapy for various neurological conditions and disorders. Such therapy provides distinct advantages over surgical lesioning techniques, which are still being used to affect disorders and conditions such as Parkinson's disease, essential tremors and dystonia. In particular, unlike surgical lesioning techniques, electrical stimulation is a reversible and adjustable procedure that provides continuous benefits as the patient's disease progresses and the patient's symptoms evolve.
Electrical stimulation of neural tissue to affect a particular neurological condition is typically performed by implanting near a specific site of neural tissue a device including an electrical lead having one or more electrodes. The lead is coupled to a signal generator that delivers electrical energy through the electrodes to the neural tissue stimulating an increase, decrease, or block of neuronal activity to directly or indirectly affect the neurological condition. In order to perform this procedure effectively, a practitioner must position the electrical stimulation device in such a way to modulate the desired volume of neural tissue and to minimize stimulating unwanted adjacent neural tissue, which could create undesirable side effects. Such precise targeting to focus stimulation towards a specific location sub-serving the desired function to be modulated requires enormous time and effort. Furthermore, often times the stimulation must be adjusted or redirected after the initial surgery as a result of sub-optimal placement, lead migration, disease progression, inefficacious treatment, undesirable side effects, neural plasticity, or histological changes of tissue surrounding the stimulation device.
With present multi-contact electrode devices, it is hard to overcome these problems since it is difficult to redirect stimulation after the initial surgery even though limited readjustments can be made by selecting a different contact combination, pulse rate, pulse width or voltage. Stimulation devices have been described to purportedly address the deficiencies of these multi-contact electrode devices, but none provide an optimal alternative. For example, U.S. Patent Publication 2002/018317 describes a directional brain stimulation lead assembly including a lead body and an insulating member defining one or more windows that selectively expose portions of electrodes carried by the lead body to produce a directional stimulation current field. Because of the configuration of the electrodes, however, the distance of electrical stimulation in the radial direction is limited. Therefore, the lead assembly may not be able to effect therapy to neural tissue sites located outside the assembly's radius of stimulation. U.S. Pat. No. 6,353,762 describes a device including electrical leads inserted into a cannula and projecting outward at the distal end of the cannula. Because the leads only project from the distal end of the cannula, the area over which stimulation can be provided is limited. For example, if it is desired to stimulate a new neural tissue site located superior or inferior to the original stimulation site, the device's position must be readjusted to raise or lower the device so that the leads are positioned in a location adjacent to this new neural site. Such readjustment may require a second surgery if the decision to reposition the device is made after the initial surgery, thereby increasing the risk of bleeding and damage to surrounding neural tissue and increasing the cost of the overall therapy.
Therefore, there is an unmet need for a versatile neural stimulation delivery device that allows for varying directions, distances, and degrees of stimulation to sufficiently reduce the time, cost, and risk of electrical stimulation of neural tissue.